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998 engine rebuild

Where did get those scratchers from? How much are they?
 

justinator said:
Theres no way to say for sure what boost level is safe for 91 all the time. Too many factors come into play......snow conditions causing extra engine load , hotter IAT's, aggressive clutch setups, minor boost leaks etc. Low boost tunes (15-15.5 psi) or less I would guess arent gonna be too fussy but only way to know is to datalog. I cant imagine spending money on tunes and hardware and clutching and spending time on testing different setups etc but not spending the extra for the datalogging. Real time info, no guessing about adequate fuel, no staring at a dash trying to watch rpms while clutching a 250/275/300hp + sled. All the data you need at your fingertips. No assuming your sleds happy with your gas choices because you dont see a knock light but in reality its pulling 1-2 degrees of timing just about every time your on it and you dont know. worth every penny all day every day.
Click to expand...
Good and valuable point! As we all have seen, not that long ago TD published "revised" octane recommendations for all of their tunes. If you look through it, you see allot more 93 and higher.
IMO - there is NO 17+ psi tune safe with 91 octane; especially for those of us who want to run several miles WFO. IMO, one would need 100 octane to run 17-18 psi of boost for 1-2 miles without hurting the engine. Even with GAP detonation prevention active, I wonder if ECU is able to reduce timing enough to prevent engine damage. IMO, even then, the BTU output of that much power for that long exceeds what the cooling system can handle. No doubt, allot can run these tunes on 91 just blipping them corner to corner. But once they get to a flowage that's 6 miles long (along the marked stakes), 91 will not work at WOT for several miles.
 
When I had the zuke engine when knock came on and if you held it longer it would shut motor down, you had to restart to get back running, I was running TD tune, never heard or seen one of these Yamaha engines doing this to save the engine.
 
This TCat owner I'm rebuilding his engine insists he only occasionally saw knock light flicker, randomly. Never came on and stayed on. He says he always let off when he saw it flicker. IMO, tells me knock protection eas not working very well at all. All 3 pistons damaged
Center piston had a small piece missing above top ring. Deto must have been bad.
 
It is my understanding that low level(but still damaging) knock can occur even without triggering the knock light. Remember, there are other noises and vibrations that are normal, yet we want the knock sensor to ignore those.
I've seen comments on these threads over the years of guys running tunes while running 87. IMO, I would never do that, even on the lower tunes. The lower HP tunes are only to run 87 in a situation when you can't get 91 or higher and if you are to run 87 on any tune 240 and under I wouldn't be holding it full throttle for prolonged periods.
 
Couple points to consider...... A tuner has to recommend an octane for the tune he creates. He has to imagine the different conditions the sled will likely see through the course of a winter. This varies from mild to wild riding, different weight riders and the list goes on and on. He probably chooses an octane that will work for the majority of riders and average conditions. Running a sled1,2 or even 3 miles wide open is not what the average rider will do through out the course of a winter. Light cruising and never going wide open is also not what the average rider will do. In those 2 cases 87 octane will work for one guy and the other will need 98. How do you perfectly recommend the perfect octane......you cant, you have to suggest what will cover most of the bases and I believe they did a good job of suggesting that or atleast the best they could. If they wanted to guarantee every tune was covered under every single condition they would have to suggest a very high octane gas that isnt available at the pumps and this isnt needed for the majority, their tunes an octane ratings are fine. Datalog your sled during your riding style and review and no where you stand and you will know if the octane your using is adequate or if it needs a little something added to the recipe or if its happier with a certain clutch setup over the other etc. I cant speak for hurricane but td has the knock light flash somewhere after 2-2.5 degrees of timing retard and I believe hurricane is similiar. They chose this configuration because its ok and it works. Every modern gas engine has experienced light knock and the ecu has done adjustments to keep it at a light, non damaging knock. If you want zero knock, zero ti ming retard in any condition then be prepared to lose all your fuel mileage and all your response and power. You cant have both all of the time. Your 2018 chevy pickup that runs happily on 87 octane gas does just that till you hook up to an 8000lb trailer on a 90 degree day and begin to climb a large hill and the knock sensor, the little tiny microphone listening for knock does its job by detecting this baby knock and correcting it before it becomes damaging knock. on this day, 91 octane would of prevented this but gm doesnt say to use 91 all the time because its not needed,the ecu did its job and prevented any damage.I have just shy of 5000 miles on td tunes, ive seen the knock light a couple of times experimenting with clutching setups. Datalogs show slight amounts of timing retard being pulled at certain times, sled has ran tunes from 17-20.6psi since it has 200 miles on the odometer. The head came off of it for arp studs and valve retainers. There is zero evidence of deto, none whatsoever. The mechanic who did the work is one of the top 10 yamaha dealer techs in the country. Been racing his whole life, knows his stuff. The gap knock protection system does its job and it works as it should and as it is advertised. Nothing in life is idiot proof but Dave and Ben have systems that work, simple as that. As far as millenium technologies claiming they are seeing lots of engine damage from all the tuners, I find that a stretch on their part. I know hurricane and td dont have customers sign contracts when buying tunes that swear them to secrecy if something happens. I dont believe that td and hurricane customers are bashful and afraid to talk. People talk the most when they are pissed. And when you burn up a sled people get pissed even if it is their own doing. The last 2 years there has been a bunch of chatter on here about engine issues and just as much on all the facebook groups and its all been focused on one tuning company. Why are we not hearing so much chatter from the other camps? or do td and hurricane customers not post on ty and arent on facebook. I find that odd as Id venture to say that 80%(likely more) of the tuned sleds are running td or hurricane. Has there been some sleds from these guys gone down? Im sure their has but its not a tune problem or knock light problem etc......its bad luck, bad gas, bad operator etc. The tunes from either of these tuners using gap are fine and ready for you to run them. If your nervous and want to feel better, run your sled and log it. Learn what it needs and enjoy it for a long time while it lives a long reliable life. No need to be nervous about blowing your sled up, just give it what it needs and it wont let you down.
 
Last edited:
Turboflash said:
This TCat owner I'm rebuilding his engine insists he only occasionally saw knock light flicker, randomly. Never came on and stayed on. He says he always let off when he saw it flicker. IMO, tells me knock protection eas not working very well at all. All 3 pistons damaged
Center piston had a small piece missing above top ring. Deto must have been bad.
Click to expand...
What tune on this one? Maybe I missed it in another post?
Definitely a pattern on the center piston here.. heat is building more in the center and causing slightly more damage.
 
jonlafon1 said:
What tune on this one? Maybe I missed it in another post?
Definitely a pattern on the center piston here.. heat is building more in the center and causing slightly more damage.
Click to expand...
PEFI Stage 3 280HP.
Center piston surrounded by other 2. More heat. Needs to be richer AFR than outside ones but PEFI Stage 3 has them all same. :(
 

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    TCat 998 head PEFI St3.jpg
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Is it the heat or the way the intake is designed?
 
Turboflash said:
PEFI Stage 3 280HP.
Center piston surrounded by other 2. More heat. Needs to be richer AFR than outside ones but PEFI Stage 3 has them all same. :(
Click to expand...
Do the other tuners compensate for the added heat in center cylinders?
 
Stock plugs in the Sidewinder are CR8E.
When I first bought and tuned my SW I switched to the colder dual electrode CR9EK plugs and regapped them to .025" not unlike what I did on my SC Apex.
Hopefully the colder plugs would help a bit with heat and detonation but ultimately lean and/or not enough octane will always do damage.
I run my sled on the SS 240 PM tune 99% of the time and only switch to the 270 or 300 tunes when racing and using high octane fuel.
 
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